Eli Manning wants his starting receivers in camp with the Giants as soon as possible.

When Eli Manning invited Victor Cruz and Hakeem Nicks to join him for some private workouts at Duke University in early April, he was hoping it would just be the start of their offseason training.

He never wanted it to be a one-shot deal.

But that’s exactly what it has become since Cruz has not been at any of the Giants’ offseason workouts while Nicks has mysteriously skipped the organized team activity (OTA) sessions without explanation for the last three weeks.

Manning, who has had to settle for throwing mostly to backup receivers, is sounding more and more unhappy about it as time goes by. “I was just really hoping (the Duke workouts) would be a little starter course to the spring, not a substitute for what we’re doing on the field right now,” Manning said after the Giants’ final OTA on Thursday. “This is stuff where we’re getting to go against cornerbacks. You get to work your technique.”

Both Victor Cruz (r.) and Hakeem Nicks have been no-shows at Giants offseason workouts.

The good news is that even though Giants coach Tom Coughlin insists he still hasn’t gotten an explanation for Nicks’ absence from the “voluntary” OTAs, the receiver is likely to be at the Giants’ mandatory full-team mini-camp next week − at least “I would expect that he would,” Coughlin said. If Nicks doesn’t show, the Giants can fine him up to $66,150 — $11,025 for the first missed day, $22,050 for the second and $33,075 for the third.

Cruz, though, “is a different category,” Coughlin said. He can’t be punished for not showing up because he’s still unsigned for the 2013 season. And Cruz will almost certainly not attend unless he decides to sign his one-year, $2.879 million tender or finalizes the long-term contract extension he’s been negotiating for months by then.

At least the Giants’ offensive trio has gotten some offseason work in, however. Back in early April, Eli and his brother Peyton held a private camp at Duke, under the watchful eye of Blue Devils coach David Cutcliffe, who was Eli’s head coach at Ole Miss and Peyton’s offensive coordinator at Tennessee. Each quarterback invited three receivers from their NFL teams. Eli was joined by newly signed Louis Murphy, Nicks and Cruz.

For now, Eli Manning is working with backup wide receivers like Brandon Myers.

Manning is hopeful that when Nicks and Cruz return for good they won’t need long to get their timing down. But he does worry that there’s no way to make up the time they’ve already missed.

“They’ve run these plays hundreds of times before, so they’ll be able to get in the flow of things,” Manning said. “But you’d still like them back here just to work on things that we didn’t do as well last year. They know what they’re doing. It’s just a matter of improving how they’re doing it sometimes.”